With a power chain saw of this type, the tube projects upwardly out of the tank, and the opening is formed by an externally threaded screw inserted in the free tube end. Fuel can discharge via this tube or the opening during an overpressure in the tank, and fresh air can be drawn in for aeration.
Although the free tube end is not in the immediate vicinity of the saw guide bar and of the motor, it is not that far from these parts that it could not be contaminated or clogged by dirt or contaminants from the surrounding air, especially by dust formation during working or the like, or by exhaust gases. The thread consequently can clog or become obstructed more or less rapidly, so that the aeration and venting of the tank is disrupted. Additionally, the thread can also become dirty or contaminated via contaminants in the fuel, because the fuel relatively frequently drips out of the passage or opening in spite of the upwardly directed position of the tube.